Carbon–Water Coupling Coordination and Its Drivers Along the Water Withdrawal–Use–Discharge Cycle: Evidence from Qinghai Province

Carbon and water systems exhibit complex synergies and trade-offs and are closely interconnected through the social water cycle. This study examines eight prefecture-level regions in Qinghai Province from 2010 to 2024. A comprehensive carbon–water evaluation system and coupling coordination degree (CCD) model were used to characterize the spatiotemporal evolution of carbon–water coupling coordination, while CatBoost-SHAP was applied to identify the main factors associated with coordination across water withdrawal, use, and discharge processes. The results show that: (1) the carbon–water CCD exhibited an overall fluctuating upward trend, with the comprehensive evaluation index of the carbon subsystem generally higher than that of the water resources subsystem; (2) coordination showed pronounced spatial heterogeneity, characterized by relative stability in high-level regions and gradual improvement in low-level regions; and (3) water resource use within the social water cycle was closely associated with carbon–water coupling coordination, with indicators related to agriculture, the forestry–animal husbandry–fishery sector, and water supply showing relatively high model importance. Accordingly, carbon–water synergistic management should improve water use efficiency in production sectors, strengthen matching between water supply and end-use demand, and implement differentiated management according to regional resource endowments, ecological functions, and socioeconomic development levels.